Ricoh D129 Service Manual page 508

Fusing overheat error 1 (software detection)
A fusing temperature (at the end) of over 230°C (446°F) is detected for 1
second by the fusing thermistors at the center or at either end of the fusing
roller.
553 A

Power supply unit defective

I/O board (IOB) defective

BCU defective

TRIAC short on PSU (PSU defective)
Fusing overheat error 1 (hardware detection)
A fusing temperature (at the end) over 250°C is detected by the fusing
554 A temperature monitor circuit in the BCU board.

I/O board (IOB) defective

BCU defective
Fusing lamp consecutive full power 1
After warm-up, the fusing lamp remains at full power for 40 seconds without
555 A the hot roller rotating.

Disconnected or defective thermistors (ends)

Defective fusing lamp
Zero cross frequency error
When the zero cross signal is 66 or more and it is detected 10 times or more
557 C in 11 detections, the machine determines that input 60 Hz and SC557
occurs.

Noise (High frequency)
SM 6-19
Service Call Conditions
D129/D130